rx.internal.operators.OnSubscribeToObservableFuture Maven / Gradle / Ivy
/**
* Copyright 2014 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.internal.operators;
import java.util.concurrent.*;
import rx.Observable.OnSubscribe;
import rx.Subscriber;
import rx.exceptions.Exceptions;
import rx.functions.Action0;
import rx.internal.producers.SingleProducer;
import rx.subscriptions.Subscriptions;
/**
* Converts a {@code Future} into an {@code Observable}.
*
*
*
* You can convert any object that supports the {@code Future} interface into an {@code Observable} that emits
* the return value of the {@code get} method of that object, by using this operator.
*
* This is blocking so the {@code Subscription} returned when calling
* {@code Observable.unsafeSubscribe(Observer)} does nothing.
*/
public final class OnSubscribeToObservableFuture {
private OnSubscribeToObservableFuture() {
throw new IllegalStateException("No instances!");
}
/* package accessible for unit tests */static class ToObservableFuture implements OnSubscribe {
final Future extends T> that;
private final long time;
private final TimeUnit unit;
public ToObservableFuture(Future extends T> that) {
this.that = that;
this.time = 0;
this.unit = null;
}
public ToObservableFuture(Future extends T> that, long time, TimeUnit unit) {
this.that = that;
this.time = time;
this.unit = unit;
}
@Override
public void call(Subscriber super T> subscriber) {
subscriber.add(Subscriptions.create(new Action0() {
@Override
public void call() {
// If the Future is already completed, "cancel" does nothing.
that.cancel(true);
}
}));
try {
//don't block or propagate CancellationException if already unsubscribed
if (subscriber.isUnsubscribed()) {
return;
}
T value = (unit == null) ? (T) that.get() : (T) that.get(time, unit);
subscriber.setProducer(new SingleProducer(subscriber, value));
} catch (Throwable e) {
// If this Observable is unsubscribed, we will receive a CancellationException.
// However, CancellationException will not be passed to the final Subscriber
// since it's already subscribed.
// If the Future is canceled in other place, CancellationException will be still
// passed to the final Subscriber.
if (subscriber.isUnsubscribed()) {
//refuse to emit onError if already unsubscribed
return;
}
Exceptions.throwOrReport(e, subscriber);
}
}
}
public static OnSubscribe toObservableFuture(final Future extends T> that) {
return new ToObservableFuture(that);
}
public static OnSubscribe toObservableFuture(final Future extends T> that, long time, TimeUnit unit) {
return new ToObservableFuture(that, time, unit);
}
}